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You can create a Nintendo Account using your smart device or computer.
Using your computer, visit https://accounts.nintendo.com to create an account.
You can also create an account from within Animal Crossing: Pocket Camp by following these steps:
■ Steps to Create a Nintendo Account
You can create an account by tapping Link Nintendo Account at the bottom of the title screen. You can also access the account-creation page by tapping Settings within the main menu, and then selecting Link Nintendo Account.
Note: You will need an e-mail address to create a Nintendo Account.
・ We recommend using an e-mail address that you will continue to use in the future.
If you lose access to your e-mail address, you may not receive important notifications.
・ If the steps above do not take you to the account-creation page, you may be signed in with another Nintendo Account. If so, please sign out and try again.
If this did not resolve your issue, you can also refer to these articles.